code: def add_label(self, label):
      label = label.lower()
      if label not in self.label2id:
          self.label2id[label] = len(self.label2id)
          self.id2label[self.label2id[label]] = label
  
      assert label == self.id2label[self.label2id[label]]
  
imports: import json
  import torch
  from torch.utils.data import Dataset
  from torch.nn.utils.rnn import pad_sequence
  import numpy
  import prettytable
  from tqdm import tqdm
  from transformers import AutoTokenizer
  import os
  from deepke.name_entity_re.standard.tools import *
  import requests
  from typing import List
  from .utils import convert_index_to_text
label_desc: Use image node_id 2 for calling the Vocabulary obj's underlying member method code with example usage: obj.add_label(label) without return types